The present invention relates to a vacuum valve with a valve housing, a continuous line, the conductance of which is to be set, in the valve housing, further a valve body movably supported extending into the line, which body, as a function of its position, predominantly defines the conductance of the line, as well as a setting device connected with the valve body.
Fundamentally vacuum valves differ constructionally from valves for other applications in that, apart from other properties, the setting device which sets the valve body or valve disk, as a unit movable with respect to the valve housing, is encapsulated away from the line. This is done in order to avoid contamination by movement abrasion, of the vacuum atmosphere in the line. This encapsulation is often carried out with the aid of a metal bellows, which is installed between the valve body, and the housing-side wall of the line. In this bellows are installed the movable parts of the setting device acting upon the valve body.
Vacuum valves are known in various structural forms of interest, in particular, in the present context in terms of their setting properties. Vacuum valves are known which can be set into two predetermined positions, namely according to the establishment of a minimum value of conductance in their closed position, and a maximum value in their open position. Such xe2x80x9cbinaryxe2x80x9d acting vacuum valves are used, for example, as Open/Close valves for purging or evacuating vacuum installations or as lock valves.
Other structural forms of vacuum valves permit the continuous adjustment from minimum conductance (closed position) to maximum conductance (open position), wherein the conductance setting in intermediate positions is not reproducible and can only be roughly estimated.
In the last listed structural form the fast opening or closing of the valves is not possible since for changing over from the one into the other extreme position a relatively long adjustment path must be traversed. If such a valve comprises, for example, a thread guidance between setting device, on the one hand, and housing, on the other hand, it is readily evident that, depending on the pitch of the selected threading, several rotations on the setting device are necessary in order to drive the valve body from the one into the other extreme position.
Such spindle valves conventionally require 5 to 15 actuation rotations in order for the valve body to traverse its complete setting displacement.
It is the task of the present invention to provide a vacuum valve by means of which precisely predetermined conductances of the valve body-set line are reproducible and rapidly settable.
This is attained in a vacuum valve of the above described type in that, along the setting displacement of the setting device, locally offset snap-in devices are effective into which snaps the setting device for predetermined setting displacement positions. The snapping-in at the particular snap-in devices is again releasable by increasing the driving force acting on the setting device.
By provision according to the invention of said snap-in devices it becomes possible to move the setting device rapidly into a snap-in position, which corresponds to a precisely predetermined valve body position and thus to a precisely predetermined resulting conductance in said line.
In a preferred embodiment of the vacuum valve according to the invention the displacement movement of the valve body is guided by means of a guidance curve on the setting device with respect to the housing. By selecting the guidance curve, the transmission of movement from the input-side driving setting extension to the output-side valve body displacement can be selected. In an embodiment that is highly preferred, according to the invention, a nonlinear transmitter is provided on the vacuum valve which transmits the driving movement at the input side with respect to the setting devicexe2x80x94as stated nonlinearlyxe2x80x94to the setting displacement for the valve body.
In this way, it becomes possible, for example, to select a dependence between input-side driving movement onto the setting device and resulting setting displacement, which dependence corresponds to a desired conductance change, for example a linear or desired progressive one.
Although the vacuum valve according to the invention can be applied in combination with an exclusively linearly movable setting device, it is highly preferred to be developed with a setting device which is driven rotationally and acts on the valve body via a threading tension curve.
Since, during the displacement of the valve body from its seat, which in the closed valve position is, for example, sealing, the conductance increase for each traversed displacement path unit initially takes place rapidly then increasingly more slowly, in a further preferred embodiment of the vacuum valve according to the invention it is proposed thatxe2x80x94viewed from a setting device position for minimum conductance (closed position) toward a setting device position for maximum conductance (open position)xe2x80x94identical setting device driving paths are converted via a nonlinear movement converter into increasing, preferably progressively increasing, valve body paths. In this way, extremely finely and identical driving movement paths, initially only slight valve body displacement paths subsequently increasingly greater ones, are realized, wherewith said conductance can also be set finely stepped, even in the only minimally opened valve body displacement range. For example, it can be adjusted to be linearly stepped.
This is preferably realized in that the setting device is rotationally driven at the input side and, via a thread guidance with a pitch varying as a function of the rotational angle, acts onto the valve body.
In particular with the preferred application of said nonlinear movement converter it is now possible to use only short input-side driving paths in order to drive the valve body from the one into the other extreme position. In a linear movement transmission between input-side driving movement and valve body displacement movement a fine setting of the conductance can only be realized through correspondingly flat transmission in which a small valve body displacement is set through relatively long input-side driving paths. When using the nonlinear transmission provided according to the invention, this can be realized over only a small input-side driving path for the setting device. But therewith simultaneously with the precise settability of the conductance, it is made possible to fully open or fully close the valve according to the invention with a short drive-side movement. This is utilized in the preferred implementation of the vacuum valve according to the invention in which the setting device is rotationally driven at the input side and the entire setting displacement of the valve body is transmitted at a driving rotational movement of maximally 270xc2x0, preferably of maximally 135xc2x0.
In a further preferred implementation, with the realization of the setting device as rotationally driven at the input side, the snap-in devices are installed as rotation angle snap-in devices in at least one plane perpendicular to the rotational axis of the input-side setting device drive, therein preferably in the form of spring-ball acceptance snap-in devices.
In order to the able in the following to carry out precisely and relatively finely graduated conductance settings on the vacuum valve in the displacement range of the valve body also, it is proposed that, viewed from a setting device position for minimum conductance (closed position) to a setting device position for maximum conductance, the local offset, with respect to the valve body displacement, of the snap-in devices is initially selected to be small and subsequently increasingly greater.
In a further preferred implementation the snap-in devices, structurally combined to form a snap-in unit, can be readily interchanged. This is possible thereby that the snap-in devices are installed on the setting device separately from movement guidances for the displacement movement of the valve body. In an especially preferred implementation of the vacuum valve, the setting device is rotationally driven at the input side and operationally connected with a manually controllable knob. This takes account of the fact that, in particular with manually adjustable vacuum valves, the desired reproducible conductance setting presents a problem.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.